Q220 · Practice questionSimple familiar1 mark
QUESTION 220
In a thin-foil scattering experiment, most positively charged alpha particles pass through, but a small fraction deflect through very large angles. Which conclusion best accounts for both observations?
(A)
Positive charge is spread uniformly throughout the atom.
(B)
Every incident particle collides with an electron.
(C)
Most of the atom is empty space, with positive charge concentrated in a small nucleus.
(D)
Electrons occupy only discrete energy levels.
WORKED SOLUTION
1 markAnswer C
ANSWER
C. Most of the atom is empty space, with positive charge concentrated in a small nucleus.
Worked solution
Most particles miss the small nucleus, so they pass through with little deflection. The intense repulsive field near a small positively charged nucleus can produce the rare large-angle deflections. The scattering result alone does not establish quantised electron energies.
Equivalent physically justified methods and consistent equivalent units accepted.
Displayed decimals are model answers; accept appropriate significant figures and consistent rounding from stated constants.
Select C.
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